Can anyone help me solve this?

a maan can cycle from his house to a railway station and back in a certain time at 12km/h. if he rides out at 8km/h and returns by motor at 15km/h, he takes 15mins longer on the double journey? Find the distance between his house and the station.

I'm not really sure how to approach this problem. Whether to name the distance x, or use the distance/time formula.

please help